The planar-type single-elemental and eight-elemental InGaAs 2.6 μm cut-off wavelength infrared detectors are fabricated on the NIN-InP/In0.82Ga0.18As/InP epitaxial materials using sealed-ampoule Zn-diffusion method.And the temperature-dependent spectral response,dark current characteristics and peak detectivity of the detectors are analyzed.The results indicate that the main resources of the forward current arise from material-defects induced generation-recombination current at lower bias under different temperatures,and as the forward voltage increases the forward current limited by the series resistance tends to be a constant.Near room temperature (>250 K),the main resources of the reverse current of the detectors are diffusion-current and generation-recombination current,and with the decline of the temperature,the tunneling-current proportional to the bias take charge.The R0A of the detectors is determined by generation-recombination mechanism above 158 K,while it is limited by traps-assisting-tunneling mechanism below 158 K.As the decrease of temperature,the peak detectivity reach a peak value of 1.7×109 cmHz1/2/W for the single-elemental detectors and 9.4×109 cmHz1/2/W for the eight-elemental detectors at 210 K.